Hydraulic fluid composition

Abstract: The present invention relates to a hydraulic fluid composition having a high boiling point, in particular a high equilibrium reflux boiling point and a low viscosity. The composition contains, as additive, at least one ether amine having a molecular weight between 120 and 300 and having the following formula : in which R₃ is linear or branched radical having at least one ether functional group and no alcohol functional group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2.

Description: The present invention relates to a hydraulic fluid composition and in particular to a brake fluid composition. The preparation is known of hydraulic fluids based on glycol ethers and/or based on boric esters of glycol ethers. These hydraulic fluids most often contain additives, in particular corrosion-inhibiting or oxidation inhibiting additives and a neutralizing agent. The preparation is known of hydraulic fluids containing amines as corrosion-inhibiting additives and/or as neutralizing agents. In particular, the use is known, according to European Patent Application EP-A-454 110 and Patent US 3 711 410, of alkanolamines. However, it was observed that these alkanolamines do not make it possible to prepare hydraulic fluids of high boiling point which simultaneously have a number of specific characteristics. In particular, they do not make it possible to prepare hydraulic fluids having a desired viscosity and optionally a desired volatility as a function of the boiling point, while moreover having good compatibility with elastomers of styrene butadiene rubber (SBR) type, a basic pH and good corrosion-inhibiting properties. The present invention relates to a high boiling point hydraulic fluid composition which makes it possible to solve the problems mentioned above. The subject of the present invention is thus a hydraulic fluid composition based on at least one glycol ether or on at least one boric ester of a glycol ether or a mixture of the two, characterised in that it contains, as additive, at least one ether-amine having a molecular weight between 120 and 300 and having the following formula: in which R 3 is linear or branched radical having at least one ether functional group and no alcohol functional group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2. According to the present invention, the composition contains an ether-amine used essentially as a corrosion-inhibiting additive and/or a neutralizing agent. This ether-amine has a molecular weight between 120 and 300. When an ether-amine is used which has a lower molecular weight, a composition is obtained which is volatile and which has a low boiling point. Moreover, when an ether-amine is used which has a greater molecular weight, a composition is obtained which has an excessively high viscosity. The molecular weight of the ether-amine is preferably from 150 to 250. According to the invention, the ether-amine used must contain a radical R3 which is a linear or branched radical having at least one ether functional group and no alcohol functional group. Thus radical R3 is not cyclic. According to one particular embodiment of the invention R3 has the following formula R1-O-R2- in which R1 is a linear or branched alkyl radical preferably having from 1 to 5 carbon atoms and R2 is a linear or branched alkylene radical preferably having from 2 to 8 carbon atoms. The ether-amine comprises at least one and preferably at least 2 units derived from an epoxide. Very advantageously, p+q ranges from 1 to 3. It is preferred to have p + q = 2. Furthermore, it is also advantageous to use a mixture comprising by weight from 85 to 95 % of an ether amine having p + q = 2 and from 15 to 5 % of an ether-amine having p + q = 3. The ether-amine is generally obtained by reacting a starting ether-amine, with an epoxide such as, for example, ethylene oxide, propylene oxide or a mixture of the two. A particularly advantageous starting ether-amine can have the following general formula (A): R 1 -O-R 2 -NH 2 in which R 1 and R 2 have the same meaning as above. The ether-amine obtained advantageously contains the amines having the following formula (B): in which R 1 , R 2 , R, p and q have the same meaning as above. In practice, a mixture of ether-amines having the formula (B) is obtained. It is desirable to obtain essentially the amine having the formula (B) in which p = 1 and q = 1. The hydraulic fluid composition according to the invention most often contains, by weight, between 0.5 and 5 %, and preferably between 1 and 4 %, of the ether-amine. The composition of the invention has generally a viscosity measured at 40°C equal to or less than 10 mm2/s, and preferably comprised between 2 and 8 mm2/s. It essentially consists of at least one glycol ether such as, for example, butyl triglycol ether, ethyl triglycol ether or methyl triglycol ether, or most often of at least one boric ester of a glycol ether such as, for example, the boric ester of methyl triglycol ether or further of a mixture of the two. When the hydraulic fluid contains a boric ester, the amine of the invention is an excellent neutralizing agent. The composition can contain the usual additives of hydraulic fluids. In particular, it can contain, in addition to the amine, a corrosion-inhibiting additive, such as benzotriazole, tolyltriazole, an alkali metal or alkaline-earth metal nitrate, triphenyl phosphite, or dodecenylsuccinic anhydride. It can also contain an oxidation-inhibiting additive such as bisphenol A or polymerized trimethylquinoline. A composition according to the invention can advantageously contain, by weight: a) from 60 to 95 % of boric ester of the monomethyl ether of triethylene glycol, b) from 1 to 15 % of monomethyl ether of triethylene glycol, c) from 0 to 15 % of monobutyl ether of triethylene glycol and d) from 0.5 to 5 % of an ether-amine according to the invention. The amine used makes it possible to more particularly obtain compositions having an equilibrium reflux boiling point (E.R.B.P.) equal to or greater than 270°C, e.g. from 270 to 295°C, and simultaneously a kinematic viscosity, measured at - 40°C, equal to or less than 1100 mm2/s, e.g. from 900 to 1100 mm2/s, while having a low volatility which is characterized by a small variation in the pH and in the reserve alkalinity (RA) after having been subjected to an evaporation test. It also makes it possible to obtain compositions having an E.R.B.P. equal to or greater than 300°C, e.g. from 300 to 310°C, while having a kinematic viscosity, measured at - 40°C, equal to or less than 1400 mm2/s, e.g. from 1250 to 1400 mm2/s. Moreover, all these compositions have a pH between 7 and 9 and preferably between 7.5 and 8.5, a good compatibility with elastomers and good corrosion-inhibiting properties, especially with respect to ferrous alloys or metals. The composition according to the invention is particularly suited to the manufacture of brake fluids of DOT 3 type (DOT signifying Department of Transportation U.S.A.) and preferably of DOT 4 or DOT 5.1. These brake fluids can be used very advantageously in the brake circuits of competition cars, in particular when they have an E.R.B.P. equal to or greater than 300°C. Measurement of the E.R.B.P. The E.R.B.P. of a hydraulic fluid is measured in °C according to the SAE standard J 1703 of June 1991. Measurement of the pH The pH of a hydraulic fluid is measured according to SAE standard J 1703 of June 1991. Measurement of the reserve alkalinity The reserve alkalinity (RA) of a hydraulic fluid is measured by the volume of 0.1 N hydrochloric acid, expressed in ml, necessary to obtain a pH of 5.5 for a 50 ml sample of hydraulic fluid. The following examples illustrate the present invention. Examples 1 to 7 7 hydraulic fluid compositions were prepared. Table 1 gives the compositions by weight. Composition 1, prepared according to the invention, contains 2,2'-[3(methoxypropyl)imino]bisethanol (amine (C)), which was obtained by reacting 3-methoxypropylamine with 2 moles of ethylene oxide. This ether-amine had the following composition by weight : The other compositions are comparative and were not prepared according to the invention. Table 2 shows, for each of the compositions 1 to 7, the following characteristics : the boron content in weight %, the pH, the equilibrium reflux boiling point (E.R.B.P.), the kinematic viscosity measured at - 40°C and expressed in mm2/s, the results of the SBR rubber swelling test carried out at 120°C and for 70 hours according to SAE standard J 1703 of June 1991. Moreover, Table 2 also shows the requirements for the characteristics measured. It was observed that Composition 1 made it possible to fulfil all these requirements. Composition 5 had an excessively large swelling of the elastomers, Composition 4 had an excessively low pH and an excessively high viscosity whereas compositions 2, 6 and 7 had an excessively low E.R.B.P. Examples 8 to 10 3 hydraulic fluid compositions were prepared. Table 3 shows the compositions by weight. Composition 8, prepared according the invention, contained 2,2'-[3(methoxypropyl)imino]bisethanol (amine (C)) used in Example 1. The other compositions are comparative compositions which had not been prepared according to the invention. In Table 3, "additives" means a mixture containing tolyltriazole, triphenyl phosphite and polymerized trimethylquinoline. This mixture is used to obtain a hydraulic fluid containing 200 ppm of tolyltriazole, 0.1 % by weight of triphenyl phosphite and 0.02 % by weight of the polymerized trimethylquinoline. Table 4 shows, for each of the compositions, the following measured characteristics with the requirements: the pH the ERBP in °C the kinematic viscosity measured at -40°C expressed in mm2/s, the pH measured after having carried out Evaporation Test No. 1, the initial reserve alkalinity, and the variation in this reserve alkalinity measured after having carried out Evaporation Test No. 2. Composition No. 8 made it possible to fulfil all the requirements. Moreover, it shows the following results of SBR swelling tests carried out according to SAE standard J 1703 of June 1991: variation in the diameter (mm): 0.74 variation in the volume (%): 9.95 variation in the hardness: -11 Moreover, the results of the corrosion tests carried out according to SAE standard J 1703 are the following: ferrous metals: less than 0.1 mg/cm2 aluminium: less than 0.1 mg/cm2 copper: less than 0.1 mg/cm2 Composition 9, which contained tridecylamine, had a pH measured after Evaporation Test No. 1 of less than 7 whereas Composition 10 showed an excessively large variation in the reserve alkalinity. In Examples 8 to 10, Evaporation Test No. 1 was carried out in the following way : 100 ml of hydraulic fluid were introduced into a 600 ml glass beaker. The beaker was then placed for 168 hours in an oven maintained at 140°C. Evaporation Test No. 2 was carried out in the following way: 200 ml of hydraulic fluid were introduced into a 500 ml round-bottomed flask with a ground neck. This roundbottomed flask was placed for 24 hours in an oven maintained at 80°C ± 2°C and under a 2 mm mercury vacuum. Compositions in weight % % 1 2 3 4 5 6 7 boric ester of the monomethyl ether of triethylene glycol 95.0 95.5 90.0 91.0 85.8 95.0 95.0 monomethyl ether of triethylene glycol 1.5 6.5 monobutyl ether of triethylene glycol 2.0 8.3 11.0 2.0 2.0 amine (C) 3.0 tributylamine 3.0 tridecylamine 3.2 dioctylamine 3.5 diisopropanolamine 3.0 monoethanolamine 0.7 3-methoxypropylamine 3.0 Characteristics Requirements 1 2 3 4 5 6 7 boron content 1.87 1.88 1.80 1.82 1.88 1.87 1.87 pH from 7 to 11 7.15 7.3 7.45 6.9 7.4 7.5 8.3 ERBP (°C) > 300 308 290 306 300 310 292 261 kinematic viscosity at -40°C(mm 2 / s ) <= 1400 1329 1470 1440 1500 1273 Results of the SBR swelling test variation in the diameter (mm) from 0.5 to 1.5 + 1.1 + 1.4 + 1.1 + 1.8 variation in the volume (%) from 1 to 16 13 17.5 13 20.6 variation in the hardness (IRDH) > - 15 - 8 - 13.5 - 10.5 - 16 Compositions in weight % Example 8 Example 9 Example 10 boric ester of the monomethyl ether of triethylene glycol 63.2 62.5 41.0 monomethylene ether of triethylene glycol 4.8 11.1 monobutyl ether of triethylene glycol 21.7 18.4 49.2 triethylene glycol 8.0 6.0 8.0 additives 1.0 1.0 1.0 amine (C) 1.3 tridecylamine 1.0 tributylamine 0.8 Characteristics Requirements Example 8 Example 9 Example 10 pH from 7 to 11 7.6 7.5 8.5 reserve alkalinity 33.6 19.6 kinematic viscosity at -40°C (mm 2 / s ) < 1100 1055 1082 pH after Test No. 1 > 7.0 7.3 6.2 RA variation after Test No. 2 in % > - 10 - 1 - 51.5 ERBP (°C) > 270 273 267 265

Claims: A hydraulic fluid composition based on at least one glycol ether or on at least one boric ester of a glycol ether or a mixture of the two, characterised in that it contains, as additive, at least one ether-amine having a molecular weight between 120 and 300 and having the following formula : in which R3 is linear or branched radical having at least one ether functional group and no alcohol functional group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2. A hydraulic fluid composition according to Claim 1, characterised in that R3 is a group having the formula R1-O-R2- in which R1 is a linear or branched alkyl radical and R2 is a linear or branched alkylene radical. A hydraulic fluid composition according to Claim 2, characterised in that R1 is a linear or branched alkyl radical having from 1 to 5 carbon atoms and R2 is a linear or branched alkylene radical having from 2 to 8 carbon atoms. A hydraulic fluid composition according to any one of Claims 1 to 3, characterised in that the ether-amine has a molecular weight between 150 and 250. A hydraulic fluid composition according to any one of Claims 1 to 4, characterised in that it contains, by weight, from 0.5 to 5 % of the ether-amine. A hydraulic fluid composition according to any one of Claims 1 to 5, characterised in that it has a viscosity, measured at 40°C, of less than 10 mm2/s. A hydraulic fluid composition containing by weight : a) from 60 to 95 % of boric ester of the monomethyl ether of triethylene glycol, b) from 0 to 15 % of monomethyl ether of triethylene glycol, c) from 0 to 15 % of monobutyl ether of triethylene glycol and d) from 0.5 to 5 % of an ether-amine and having a molecular weight between 120 and 300 and the following formula: in which R 3 is linear or branched radical having at least one ether functional group and no alcohol functional group, R is a methyl radical or a hydrogen atom, p is an integer from 1 to 3 and q is an integer from 0 to 2. A hydraulic fluid composition according to Claim 7, characterised in that R3 is a group having the formula R1-O-R2- in which R1 is a linear or branched alkyl radical having from 1 to 5 carbon atoms and R2 is a linear or branched alkylene radical having from 2 to 8 carbon atoms. A hydraulic fluid composition according to any one of Claims 1 to 8, characterised in that it has an equilibrium reflux boiling point (E.R.B.P.) equal to or greater than 270°C and a viscosity measured at - 40°C, equal to or less than 1100 mm2/s. A hydraulic fluid composition according to any one of Claims 1 to 8, characterised in that it has an equilibrium reflux boiling point (E.R.B.P.) equal to or greater than 300°C and a viscosity measured at - 40°C, equal to or less than 1400 mm2/s.

Inventors: GILLMANN ANDRE, GILLMANN, ANDRE
Applicants: BP CHEM INT LTD, BP CHEMICALS SNC, BP CHEMICALS LIMITED, BP CHEMICALS S.N.C.
Application year: 1994
Main classification: C10M133
IPC codes: C10M169, C10M133